The linear model represents the height, f(x), of a water balloon thrown off the roof of a building over time, x, measured in seconds:
A linear model with ordered pairs at 0, 60 and 2, 80 and 3, 80 and 4, 20 and 6, 0 and 7, 0 and 8, 0. The x axis is labeled Time in seconds, and the y axis is labeled Height in feet.
Part A: During what interval(s) of the domain is the water balloon's height increasing? (2 points)